Abstract 190: Deletion Of Shp-1 Prevents Diabetes-induced Endothelial Cell Senescence And Restores Blood Flow Reperfusion Following Ischemia

Introduction: Ischemia due to narrowing of the femoral artery and distal vessels is also a major cause of peripheral arterial disease and morbidity affecting patients with diabetes. Diabetes-induced premature senescence of endothelial cells has been shown as a potential mechanism of poor angiogenic response to ischemia. Our laboratory has previously shown that hyperglycemia reduced vascular endothelial growth factor (VEGF) activity in ischemic muscle of diabetic mice, which was associated with increased SHP-1 expression, a protein tyrosine phosphatase. The objective of this study is to evaluate the impact of SHP-1 deletion on endothelial cell function and senescence both in vitro and in vivo .

Methods: Non-diabetic (NDM) and 3 months diabetic (DM) mice with deletion of SHP-1 specifically in endothelial cells (EC) were used. Ligation of the femoral artery was performed, and blood flow reperfusion was measured by laser Doppler for 4 weeks. Primary EC were exposed to normal (5.6 mM; NG) or high glucose concentrations (25 mM; HG) for 48 h, in normoxia (20% oxygen) or hypoxia (1%) for the last 16h in presence of VEGF.

Results: Blood flow reperfusion and limb function (voluntary running wheel) were reduced by 50% and 91%, respectively in DM mice as compared to NDM mice. Specific EC deletion of SHP-1 restored blood flow reperfusion by 55%, limb function by 37% and capillary density in DM mice. Moreover, ablation of SHP-1 only in EC prevented diabetes-induced p21 expression and reduction of Nrf-2. In cultured EC , overexpression of dominant negative of SHP-1 prevented HG-induced inhibition of proliferation, migration, and VEGFR2/Akt phosphorylation following VEGF stimulation. In addition, the expression of senescence markers (increased p21 and beta-galactosidase; reduced Nrf-2) in EC exposed to HG levels were reversed by overexpression of SHP-1 dominant negative.

Conclusion: Ablation of SHP-1 expression in EC resulted in the prevention of hyperglycemia-induced EC senescence, reduction of VEGF actions, poor collateral vessel formation and blood flow reperfusion.

Fish oil replacement prevents, while docosahexaenoic acid-derived protectin DX mitigates end-stage-renal-disease in atherosclerotic diabetic mice

Diabetic nephropathy (DN) remains the major cause of end-stage renal disease (ESRD). We used high-fat/high-sucrose (HFHS)-fed LDLr^-/- /ApoB^100/100 mice with transgenic overexpression of IGFII in pancreatic β-cells (LRKOB100/IGFII) as a model of ESRD to test whether dietary long chain omega-3 polyunsaturated fatty acids LCω3FA-rich fish oil (FO) could prevent ESRD development. We further evaluated the potential of docosahexaenoic acid (DHA)-derived pro-resolving lipid mediators, 17-hydroxy-DHA (17-HDHA) and Protectin DX (PDX), to reverse established ESRD damage. HFHS-fed vehicle-treated LRKOB100/IGFII mice developed severe kidney dysfunction leading to ESRD, as revealed by advanced glomerular fibrosis and mesangial expansion along with reduced percent survival. The kidney failure outcome was associated with cardiac dysfunction, revealed by reduced heart rate and prolonged diastolic and systolic time. Dietary FO prevented kidney damage, lean mass loss, cardiac dysfunction, and death. 17-HDHA reduced podocyte foot process effacement while PDX treatment alleviated kidney fibrosis and mesangial expansion as compared to vehicle treatment. Only PDX therapy was effective at preserving the heart function and survival rate. These results show that dietary LCω3FA intake can prevent ESRD and cardiac dysfunction in LRKOB100/IGFII diabetic mice. Our data further reveals that PDX can protect against renal failure and cardiac dysfunction, offering a potential new therapeutic strategy against ESRD.

Mice lacking angiotensin type 2 receptor exhibit a sex-specific attenuation of insulin sensitivity

The renin-angiotensin system modulates insulin action. Pharmacological stimulation of angiotensin type 2 receptor (AT2R) was shown to have beneficial metabolic effects in various animal models of insulin resistance and type 2 diabetes and also to increase insulin sensitivity in wild type mice. In this study we further explored the role of the AT2R on insulin action and glucose homeostasis by investigating the glycemic profile and in vivo insulin signaling status in insulin-target tissues from both male and female AT2R knockout (KO) mice. When compared to the respective wild-type (WT) group, glycemia and insulinemia was unaltered in AT2RKO mice regardless of sex. However, female AT2RKO mice displayed decreased insulin sensitivity compared to their WT littermates. This was accompanied by a compensatory increase in adiponectinemia and with a specific attenuation of the activity of main insulin signaling components (insulin receptor, Akt and ERK1/2) in adipose tissue with no apparent alterations in insulin signaling in either liver or skeletal muscle. These parameters remained unaltered in male AT2RKO mice as compared to male WT mice. Present data show that the AT2R has a physiological role in the conservation of insulin action in female but not in male mice. Our results suggest a sexual dimorphism in the control of insulin action and glucose homeostasis by the AT2R and reinforce the notion that pharmacological modulation of the balance between the AT1R and AT2R receptor could be important for treatment of metabolic syndrome and type 2 diabetes.

Abstract 680: Specific Deletion of SHP-1 in Smooth Muscle Cells Restores PDGF Action in Diabetes

Introduction: Ischemia due to narrowing of the femoral artery and distal vessels is also a major cause of peripheral arterial disease and morbidity affecting patients with diabetes. Our laboratory has previously shown that hyperglycemia reduced platelet-derived growth factor (PDGF) activity in ischemic muscle of diabetic mice, which was associated with increased SHP-1 expression, a protein tyrosine phosphatase. The objective of this study is to evaluate the impact of SHP-1 deletion in smooth muscle cells both in vitro and in vivo.

Methods: Non-diabetic (NDM) and 3 months diabetic (DM) mice with deletion of SHP-1 specifically in smooth muscle cells (SMC) were used. Ligation of the femoral artery was performed and blood flow reperfusion was measured by laser Doppler for 4 weeks. Primary SMC were exposed to normal (5.6mM; NG) or high glucose concentrations (25mM; HG) for 48h, in normoxia (20% oxygen) or hypoxia (1%) for the last 24h in presence of PDGF, a pro-angiogenic factor.

Results: Blood flow was recovered to 47% in DM mice compared to 80% in NDM mice. Specific SMC deletion of SHP-1 enhanced reperfusion in NDM and DM mice up to 78% and 67%, respectively. In culture, PDGF-induced proliferation, migration, and Akt phosphorylation were reduced by 69%, 50% and 40%, respectively in SMC exposed to HG+hypoxia. Inhibition of PDGF actions was associated with increased SHP-1 phosphatase activity (40%) and enhanced interaction of SHP-1 with the PDGF receptor-β (5.6-fold). Overexpression of the dominant negative form of SHP-1 restored PDGF-induced proliferation and migration as well as Akt and ERK phosphorylation in SMC exposed to HG+hypoxia.

Conclusion: High glucose level induced SHP-1 activity and caused inhibition of PDGF pro-angiogenic actions in SMC, whereas the deletion of SHP-1 specifically in SMC restored blood flow reperfusion in diabetes.